Various types of devices employ electrode gaps to achieve various objectives. There are, for example, the devices illustrated and described in U.S. patents and published patent applications: U.S. Pat. Nos. 5,887,554; 5,437,250; 5,425,332; 5,409,784; U.S.-2003-0143445-A1; U.S.-2003-0143442-A1; and, U.S.-2003-0140622-A1. The disclosures of these references are hereby incorporated herein by reference. This listing is not intended to be a representation that a complete search of all relevant art has been made, or that no more pertinent art than that listed exists, or that the listed art is material to patentability. Nor should any such representation be inferred.